The periodic paralyses are rare neuromuscular diseases which were among the first channelopathies to be defined by their specific gene mutations. The periodic paralyses have overlapping clinical phenotypes but remarkably, the causative gene lesions involve Na, K, Ca, and CI channels. Despite the wealth of information on the pathophysiology of each periodic paralysis there remain many questions concerning the phenotypic variation of patients with similar or even identical mutations. The periodic paralyses are genetically heterogeneous and there continue to be many patients with periodic paralysis whose mutations have not been discovered. While there are no approved or standard treatments for any periodic paralysis, there are a number of logical candidates suitable for clinical trials. NINDS has funded a multicenter, randomized, controlled trial of treatment of hyperkalemic and hypokalemic periodic paralysis that will begin enrollment soon. Moreover, an ORD/NINDS-funded project is focused on developing novel treatments for the recently-characterized periodic paralysis, Andersen-Tawil syndrome. This grant requests support for a two-day meeting to be held in Bethesda, MD that will bring together international basic, clinical neuroscientists and representatives of lay organizations with a research focus on the periodic paralyses. The meeting's goals will be (1) to summarize the current understanding of the pathophysiology of the periodic paralyses and focus on unresolved dilemmas concerning their pathogenesis; (2) to consider the rationale for various treatment strategies; (3) and consider how the relatively well understood periodic paralyses can inform the broader field of channelopathy research. [unreadable] [unreadable]